Objective      To study the effects of TBX21 gene T-1993C polymorphism on T-bet expression and type 1 helper T cell (Th1) polarized population.     Methods      The cis-acting regulation at-1993T/C site of TBX21 gene promoter region was studied with electrophoretic mobility shift assay (EMSA). TBX21-1993 site genotyping was conducted

via

PCR-RFLP using whole blood specimens collected from healthy volunteers. The expression levels of T-bet and Th1 polarization-associated cytokine IFN-γ in individuals with different genotypes were tested with

flow cytometry.     Results      TBX21-1993TT and TBX21-1993CC probes specifically bound with an unknown nuclear factor that had higher affinity to C allele than T allele. The expression levels of T-bet and IFN-γ in individuals with different genotypes showed an order of TT>TC>CC

with significant difference (

P

<

0.05).      Conclusion     The -1993 site is important to gene TBX21. An unknown nuclear factor can specifically bind with -1993 site T/C alleles and negatively regulate the expression of T-bet and IFN-γ

so as to affect Th1 differentiation.